Contact-less ignition system



Jan. 2; 1968 RYOJI KASAMA ETAL 3,36

CONTACT-LESS IGNITION SYSTEM Filed Aug. 26, 1965' 3 Sheets-Sheet 1 2F762 *5. F/G3 F/(i 4 F/G 5 F/6T6 F/G 7 3 6 mp1 5 a ,4 a 5 4' 5 INVENTORS03i Kasa Sai Suda.

ATTORNEY Jan. 2; 1968 RYOJI KASAMA ETAL 3,

CONTACT-LESS IGNITION SYSTEM Filed Aug. 26, 1965 3 Sheets-Sheet 2 v 5634 58 C 56 C C 570) .i 560 566' INVENTOR5 R3035 Kesama, 613i Sudcs.

ATTORNEY Jan. 2, 1968 mo. KASAMA ETAL 3,3 3

CONTACT-LESS IGNITION SYSTEM 3 Sheets-Sheet Filed Aug. 26, 1965 Ang/e 0frofaf/bn INVENTORS R c M 5&3! 3

PCLMKQ, an.

ATTORNEY United States Patent 3,361,123 CONTACT-LESS IGNITION SYSTEMRyoji Kasama and Seiji Suda, Hitachi-shi, Japan, assigmors to Hitachi,Ltd., Tokyo, Japan Filed Aug. 26, 1965, Ser. No. 482,768 Claimspriority, application Japan, Aug. 28, 1964, 39/ 48,416 4 Claims. (Cl.123-148) ABSTRACT OF THE DISCLOSURE This invention relates to acontact-less ignition apparatus for the ignition coil of an internalcombustion engine and comprises an ignition point detecting deviceformed of a U-shaped supporting member of insulating material. First andsecond air coupled coils are secured to opposite inner surfaces of thesupporting member and are electromagnetically coupled to each other onlythrough a relatively large air gap. A high frequency source ofoscillations is connected to one of the coils and a pulse shapingcircuit is connected to the remaining coil. A rotary screening memberdriven by the engine is interposed between the first and second couplingcoils for periodically screening between the coils and substantiallyreducing the high frequency energy transmitted from the first couplingcoil to the second coupling coil by means of absorption of the highfrequency energy in the rotary screening member.

The present invention relates to contact-less ignition systems.

With the rate of revolution of engines for automobiles becomingincreasingly higher these days, the ignition systems of the type whereinthe primary current of an ignition coil is interrupted by the action ofthe contact of a contact breaker are being replaced progressively byignition systems of the contact-less type using transistors. In suchcontact-less ignition systems, a small-sized A.C. generator orphototransistor, which is adapted to operate in association with therotation of an engine, is used for detecting the ignition point, and theprimary current of an ignition coil is current interrupted byinterrupting transistors connected to the ignition coil. Proper timingof the point of interruption is achieved by means of the output of saidgenerator or phototransistor.

Ignition systems using a small-sized A.C. generator, however, have thedrawback that the output of the generator is not stabilized until therate of revolution of the engine rises to a certain level, because suchsystems are operated utilizing an electromotive force e, that isproportional to and the value of d s dt increases in proportion to therate of revolution of the rotor of the generator. Furthermore, thewaveform of the output varies greatly between the operations at a lowspeed and at a high speed, therefore when the rate of revolution of thegenerator is low, the output voltage thereof is extremely low, making itditficult to use for the detection of the ignition point. In addition tothe above, the phase of the output current drawn from the generator lagswith respect to that of the output voltage generated in the generator,because the generator comprises an inductive component. Such a lag inphase becomes progressively greater with increasing frequency of thecurrent generated, which in turn will cause delay in ignition time ofthe ignition system, and thus makes the detection and adjustment of theignition point diflicult.

Turning now to the ignition system wherein a phototransistor is used asmeans for detecting the ignition point, while it is possible to obtain asubstantially constant output with respect to the ignition point ofengine, independently of the number of rotations and hence of enginespeed, there is the drawback that, when the ignition system is used forautomobiles, it is virtually impossible to obtain a long lasting lightsource whose intensity does not vary greatly with age, which is requiredfor properly controlling the phototransistor.

The present invention has been achieved with a view to obviating theforegoing drawbacks, and an object of the present invention, therefore,is to provide an ignition systern wherein a constant interrupted currentis supplied to an ignition coil, independently of the rpm. of engines.This is achieved in the present invention by introducing the output frommeans for generating high frequency current independently of the rate ofrotation of the engine to a first coupling coil for controlling theinductive voltage of a second coupling coil. The second coupling coil isdis posed opposite to said first coupling coil, and its output iscontrolled by means of a rotary plate adapted to operate in associationwith the rotation of the engine and to cross the interspace between saidfirst and second coupling coils at a predetermined interval of angle ofrotation. The form of the signal voltage of the second coil then isshaped into a pulse wave through a waveform shaping circuit, andamplified to control the primary current of the ignition coil.

Another object of the present invention is to provide an ignition systemwhich com-prises an ignition point detecting device having a firstcoupling coil connected to the output end of means for generating highfrequency current and a second coupling coil disposed opposite to saidfirst coupling coil with a rotary plate intervening therebetween. Therotary plate is adapted to rotate in association with the rotation ofengine and the second coupling coil is connected to a waveform shapingcircuit, and a constant voltage source, the output-voltage thereof beingaltered according to the rpm. of the engine. This ar rangement isconnected to the terminal of a power source whereby change in theinductive voltage of said second coupling coil is controlled inaccordance with the increase in rate of revolution of the engine, thusadvancing the ignition point automatically.

A still further object of the present invention is to provide anignition system comprising an ignition point detecting device having afirst coupling coil connected to the output end of means for generatinghigh frequency current and a second coupling coil disposed opposite tosaid first coupling coil with a rotary plate intervening therebetween.The rotary plate is adapted to rotate in association with the rotationof the engine and the inductive voltage of the second coupling coil isintroduced to an ignition coil through a waveform shaping circuit and anamplifying circuit. In this arrangement the width of the rotary plate isvaried to adjust the voltage generated in said second coupling coil,whereby the angle of flowing the primary current through the primarywinding of said ignition coil is controlled.

The present invention will be illustrated in further detail hereinafterby way of an embodiment shown in the drawings, in which FIG. 1 is ablock diagram of an ignition point detecting device;

FIGS. 2 through 4 show waveforms at various portions of the ignitionpoint detecting device;

FIG. 5 is a front elevational view of said detecting device;

FIG. 6 is a plan view of the same;

FIG. 7 is a plan view of a rotary plate as rotated at 45 degrees;

FIG. 8 is a characteristic chart illustrating the change in signalvoltage of the ignition point detecting device of FIG. 4;

FIG. 9 is a plan view of a modification in shape of the rotary plate;

FIG. 10 is another block diagram showing an embodiment of the presentinvention;

FIG. 11 is the electrical connection drawing of the device of FIG. 10;

FIG. 12 is the electrical connection drawing of another embodiment ofthe constant voltage source shown in FIG. 11; and

FIG. 13 shows voltage waveforms at various portions of the circuit shownin FIGURE 12.

Referring to FIG. 1, reference numeral 1 indicates an ignition pointdetecting device which comprises high frequency generating means 2having a constant frequency and a constant amplitude independently ofthe rotation of the engine, a first coupling coil 3 connected to theoutput end of said high frequency generating means 2 and a secondcoupling coil 4. The voltage induced in said second coupling coil 4 isamplified in a suitable amplifier of conventional construction and usedas an output signal.

The coupling coils 3 and 4, as shown in FIGS. 5 to 7, are mounted on aninsulating member 5 in opposed relation to each other, and a rotaryplate 6 is disposed between said coils so as to cross the interspacebetween the coils at a predetermined time interval.

As shown in FIGURE the output of such an ignition point detecting device1 is connected to a waveform shaping circuit '7 which is energized incommon with device 1 from a constant voltage source means 8. The outputfrom wave shaping circuit 7 is amplified through an amplifying circuit 9and connected to the primary coil of an ignition coil 10.

The waveform shaping circuit 7 serves to shape the form of output signalof the detecting device 1 into a rectangular waveform or a pulsewaveform having a short rise and fall time, and is composed of Schmitttrigger circuit or a monostable multivibrator circuit.

The constant voltage source means 8 serves to maintain the voltageapplied to ,said waveform shaping circuit 7 and the ignition pointdetecting device 1 constant.

The amplifying circuit 9 amplifies the output of the waveform shapingcircuit 7 to introduce it into the ignition coil 10 and is composed of aDO. amplifying circuit or an amplifying circuit of thecondenser-discharge type wherein a voltage raised by a D.C.-D.C.converter is led into a condenser to charge the same and the electriccharge thereof is utilized.

The present invention having such a construction as described above willbe further explained with reference to the electrical connection diagramshown in FIG. 11.

Reference numeral 1 indicates the ignition point detecting devicecomprising the high frequency generating means 2 having the firstcoupling coil 3, and the second coupling coil 4. The first coupling coil3 of the high frequency generating device 2 has its one end connected toa terminal A of a battery or power source 12 through the collector38c-emitter 382 of a transistor 38 and the other end to a terminal B ofthe power source through a collector 13cemitter 136 of a transistor 13and a resistor 14. A resistor 15 and a condenser 16 arranged in parallelthereto are connected between a base 13b of transistor 13 and one end ofthe coupling coil 3. Furthermore, between the emitter 13e-collector 130there is connected a condenser 17. A resistor 18 having its one endconnected to the terminal B of the power source is connected to saidresistor 15 in series. A condenser 19 has one end connected to theemitter 13s, with the other end connected to one end of the couplingcoil 3.

One end of the second coupling coil 4, arranged opposite to said firstcoupling coil 3 is connected to a base 2% of a transistor 23, with theother end connected to the terminal B of the power source through aresistor 21 and a condenser 22 arranged in parallel thereto. An emitter20a of the transistor 20 is connected to the terminal B of the powersource, while a collector 290 of the same is connected to the terminal Aof the power source through a resistor 23, a condenser 24 and thecollector 38cemitter 382 of the transistor 38.

Reference numeral 7 indicates the wave form shaping circuit for shapingthe waveform of induced voltage in the coupling coil 4 into a pulsewaveform, said shaping circuit comprising transistors 25 and 26 havingrespective emitters 25c and 26e connected to the terminal B of the powersource through a common resistor 27. A base 25b of the transistor 25 isconnected to the collector 200 of transistor 2t of said ignition pointdetecting device 1 through a resistor 28, while a collector 250 isconnected to the terminal A of the power source through a resistor 29and the collector 38c-emitter 38a of the transistor 38. On the otherhand, a base 26b of the other transistor 26 is connected to thecollector 250 of said transistor 25 through a resistor 30 and acondenser 31, and at the same time it is connected to the terminal B ofthe power source through a resistor 32, and a collector 260 is connectedto the terminal A of the power source through a resistor 33 and thecollector 38c--ernitter 38c of the transistor 38.

The constant voltage source means 8 has a resistor 34 which is connectedbetween the collector 380 of the transistor 33 and the terminal B of thepower source. An emitter 36c of a transistor 36, whose base 36b isconnected to an intermediate terminal of the resistance 34, is connectedto the collector 380 of transistor 38, whose emitter 38c-collector 380are connected in series to the power source, through a Zener diode 37.The emitter 36@ of the transistor 36 also is connected to the terminal Bof the power source through a resistor 39, while the collector 36c ofthe transistor 36 is connected to the base 381) of the transistor 38.

Reference numeral 9 is the amplifying circuit which comprises a Zenerdiode 39 having one end connected to the output terminal of saidwaveform shaping circuit 7, i.e., to the collector 260 of transistor 26and with the other end connected to a base 41b of a first transistor 41through a resistor 40. The collector 410 of the transistor 41 isconnected to the terminal A of the power source through a resistor 42.Reference numeral 43 indicates a transistor 43 of the second stage,whose base 43b is connected to the emitter 41a of transistor 41 of theprevious stage and at the same time connected to the terminal B of thepower source through a resistor 44. The collector 43c of transistor 43is connected to the terminal A of the power source through a resistor45. A transistor 45 which is connected in series to the primary coil 11of an ignition coil 10, has its base 461; connected to emitter 43a oftransistor 43 of the previous stage and to the terminal B of the powersource through a resistor 47, while its collector 46c is connected tothe terminal A of the power source through primary coil 11 and aresistor 48. A secondary coil 49 of the ignition coil 10 is connected atone end to the primary coil 11 and at the other end to the terminal B ofthe power source through an ignition plug Stl.

In one embodiment of the system of the present invention having such aconstruction as described above, a high frequency current having aconstant amplitude as shown in FIG. 2 is introduced into the firstcoupling coil 3 which is coupled to the second coupling coil throughonly an air path. First coil 3 is connected to the output end of thehigh frequency generating means 2 of the ignition point detecting device1 and the voltage induced in the second coupling coil 4 by the highfrequency electromagnetic energy of the first coupling coil 3 isamplified for use as an output signal. The coupling coils 3 and 4 aremounted on the member 5 of insulating material in opposed relation toeach other and the rotary plate 6 is provided between these coils, whichcrosses the interspace between said coils at a constant interval ofangle of rotation so as to screen the high frequency electromagneticenergy of the first coupling coil 3, as shown in FIGS. 5 through 7.Hence, when the rotary plate 6 is in the position shown in FIG. 7, aconstant induced voltage as determined by the shape and position of thecoupling coils 3 and 4 is induced in the second coupling coil 4. Next,when the rotary plate 6 comes to the position as shown in FIG. 6relative to the coupling coils 3 and 4, the high frequencyelectromagnetic energy of the coupling coil 3 is attenuated ordisappears by being screened by the rotary plate 6 and thus the inducedvoltage of the second coupling coil 4 is reduced.

This disappearance or attenuation of the high frequency energy is notdue to any shunt effect of the rotary plate 6 but due to absorption ofthe high frequency energy in the rotary plate 6. This can be betterunderstood from an examination of FIG. 5 through FIG. 7. When a part ofthe rotary plate 6 which is of conductive material is interposed betweenthe coupling coils 3 and 4, eddy currents are produced therein thatproduce magnetic fluxes that counteract the high frequency magneticenergy of coil 3. Consequently, transmission of the high frequencyenergy to coil 4 is screened or interrupted and there ap pears an outputsignal in the second coupling coil 4 as shown in FIG. 3.

In this case, the magnitude of the induced voltage of the coupling coil4 is not in proportion to the rpm. of the engine, as in the case of theA.C. generator, but it is determined by the oscillation frequency of thehigh frequency generating means 2. Furthermore, since the oscillationfrequency is so high and constant that the maximum amplitude of saidinduced voltage is not influenced by the rate of the rotation of rotaryplate 6, it is possible to make the voltage a modulated amplitude asshown in FIG. 3. Therefore, the signal voltage as shown in FIG. 4 can beobtained by detecting and amplifying the induced voltage. This signalvoltage is led into the waveform shaping circuit 7, comprising thetransistors 25 and 26, to convertthe same into a rectangular pulsesignal, whereby the'trans'istors '41 and 43 in the amplifying circuit 9as well as the transistor 46 connected in series to the primary coil 11of the ignition coil 10 are controlled to interrupt the collectorcurrent of the transistor 46 and to interrupt the primary current in theignition coil 10, and a high voltage thus induced in the secondarywinding is fed to the ignition plug 50 to cause a spark discharge.

According to the contact-less ignition system as has been describedhereinbefore, a high frequency electromagnetic energy is caused to betransmitted from the coil 3 to the coil 4 opposing each other in theignition point detecting device and a signal voltage is obtained byscreening the transmission of high frequency electromagnetic energy bythe rotary plate which crosses the interspace between said couplingcoils at a predetermined time interval. There are advantages, therefore,that the ignition time is not substantially retarded and that, since theinduced voltage generated in the second coupling coil 4 always producesa constant magnitude voltage without being influenced by the rate ofrotation of the rotary plate 6, the ignition of an engine can beeffected in a stabilized manner.

It is also possible, by the use of a constant voltage source, shown inFIG. 12, in place of the constant voltage source 8, shown in FIG. 11, toadvance the ignition time electrically in accordance with the rpm. ofthe engine. This is achieved by connecting terminals a, b and c to theterminals a, b and c in FIG. 11 respectively, while connecting d, e andf to d, e and 1 respectively, whereupon an emitter 51a of a transistor51 is connected to the collector 38c of the transistor 38, a collector51c to the terminal B of the power source through a resistor 52, and abase 51b is connected to the collector 26c of transistor 26, whichconstitutes the output end of the waveform shaping circuit 7, through aresistor 53 and also connected to a diode 54. The diode 54 has one endconnected to the output end of the waveform shaping circuit 7, with theother end connected to the terminal B of the power source through avariable resistor 55 and a base 56b-emitter 56e of a transistor 56.Reference numeral 57 indicates a transistor whose base 57b is connectedto the collector 510 of transistor 51 through a resistor 58, while itsemitter 57e is connected to the terminal B of the power source and acollector 570 to the cathode of the diode 54 through a resistor 59. Acondenser 60 is connected between the emitter 57a of said transistor 57and the cathode of diode 54. A collector 56c of the transistor 56 isconnected to the terminal A of the power source through a resistor 61and the transistor 38 and also to a base 63b of a transistor 63 througha variable resistor 62. Between an emitter 63c and a collector 63c ofthe transistor 63, there is connected a Zener diode 37. A resistor 34,connected between the terminal B of the power source and the collector380 of the transistor 38 has the base 36b of transistor 36 connectedthereto at the intermediate terminal 35. The transistor 36 has itsemitter 362 connected to the collector 38a of transistor 38 through saidZener diode 37, and also to the terminal B of the power source throughthe resistor 39. The collector 360 of the transistor 36 is connected tothe base 38b of said transistor 38, and the output end of the waveformshaping circuit 7 is connected directly to the terminal e to which theamplifying circuit 9 is connected.

In the system of the present invention above described, the output endof the waveform shaping circuit 7 is connected to the transistor 51 anddiode 54. The transistor 51, when the primary current of ignition coil10 is interrupted, serves to short both ends of the condenser 60 withthe transistor 57 and to convert the polarity of the output wave ofwaveform shaping circuit 7, providing for the next charging period.

The output of waveform shaping circuit 7 charges the condenser 60through the diode, instantaneously as a current begins to flow in theprimary coil 11 of the ignition coil 10. As the terminal voltage of thecondenser 6t! rises and the transistor 56 is rendered. conductive withan elevated base electric potential, a voltage drop occurs at theresistor 61 to permit a base current of the transistor 63 to flowthrough the variable resistor 62, thereby rendering transistor 63conductive. This means that the zener diode 37, which is used as areference voltage source for the constant voltage source means 8, isshortened, and as a result, the electric potential of the emitter 36c oftransistor 36 is elevated, with the collector current, i.e. the basecurrent of the transistor 38, decreasing, which results in a greaterinternal resistance and greater voltage drop in the transistor 38.

The pulse duration of output waveform of the waveform shaping circuit 7varies in accordance with the rpm. of engine, and is represented bychange in electric charge in the condenser 60 or change in terminalvoltage of the condenser 60. With the terminal voltage of condenser 60fully saturated, a minimum voltage required for the operation of thepoint detecting device is set by the output voltage of the constantvoltage source means 8. When the number of revolutions becomes high, thepulse duration of the output wave of waveform shaping circuit 7 becomessmall, the terminal voltage of condenser 60 is lowered, the internalresistance of transistor 63 is increased, the electric potential of theemitter 36a of transistor 36 is lowered, the collector current isincreased and the internal resistance of transistor 38 is reduced, andconsequently the output voltage of the constant voltage source means 8becomes high.

Hence, the output waveform of the point detecting device 1 varies asshown in FIG. 8 and such variation is demonstrated as an advance in theignition time. Namely, as shown in FIG. 13, when the r.p.m. of engineincreases from 11 to I1 and to 12 the pulse duration of the outputwaveform of waveform shaping circut '7 becomes smaller, with theterminal voltage of condenser 60 changing as shown at V and the outputvoltage of constant voltage source means 8 changing as shown at V Inconsequence, the output waveform of detecting device 1 changes as shownat V while the output waveform of waveform shaping circuit 7 changes asshown at V resulting in change in the interrupting point of the primarycurrent of ignition coil 10. It is thus, possible to advance theignition point.

As has been described above, in the system of the present invention, theoutput waveform of the ignition point detecting device is changed bychanging the high frequency electromagnetic energy of the coupling coilof said device by means of the constant voltage source means by means ofwhich output is changed corresponding to the rpm of engine. The pulseduration of the output wave of waveform shaping circuit is changed alsoin accordance with the r.p.m. of engine, and the pulse is introducedinto the ignition coil through the amplifying circuit to control theprimary current thereof. Since the ignition point is advancedelectrically and automatically in accordance with the r.p.m. of engine,it is possible to eliminate unsatisfactory advancing of the ignitionpoint due to friction or others as is encountered with a mechanicaladvancing device and also to effect automatic advancing of the ignitionpoint simultaneously with the detection of the same.

Moreover, since the time of screening the high frequency electromagneticenergy of the first coupling coil can be changed by modifying the shapeof rotary plate which crosses the interspace between the coupling coils,as shown in FIG. 9, it is possible to change the flow angle of theprimary current flowing in the primary coil of ignition coil accordingto the shape of the rotary plate.

What is claimed is:

1. A contact-less ignition apparatus for the ignition coil of aninternal combustion engine comprising:

an ignition point detecting device having a U-shaped supporting memberof magnetically insulating material;

first and second coupling coils secured to the opposite inner surfacesof the supporting member and electroma-gnetically coupled to each otheronly through a relatively large air gap;

a high frequency generating means coupled to the first coupling coil forsupplying therewith a high frequency current;

a rotatable screening means driven by the engine and disposed betweenthe first and second coupling coils for periodically screening betweenthe coils and substantially reducing the high frequency energytransmitted from the first coupling coil to the second coupling coil bymeans of absorption of the high frequency energy in the rotatablescreening means; and pulse shaping circuit means coupled to the secondcoupling coil and the ignition coil for producing a pulse according tothe output of the second coupling coil and controlling the primarycurrent of the ignition coil in accordance with the pulse.

2. A contact-less ignition apparatus according to claim 1 furtherincluding means for supplying a constant energization voltage connectedin common to said ignition point detecting device and to said pulseshaping circuit.

3. A contact-less ignition system according to claim 2 wherein means areprovided for altering the output voltage of the means for supplying aconstant energization voltage according to the r.p.m. of the engine sothat the change in inductive voltage of said second coupling coil iscontrolled in accordance with the increase in r.p.m. of the engine tothereby advance the ignition point automatically.

4. A contact-less ignition system according to claim 2 wherein thepulsed output voltage generated in said second coupling coil iscontrolled by changing the width of said rotatable screening meanswhereby the current angle of the primary current flowing in the primarywinding of the ignition coil is controlled.

References Cited UNITED STATES PATENTS LAURENCE M. GOODRIDGE, PrimaryExaminer.

